I had the same problems with mine up until about a week ago. I read an article that stated it wasn't the phones problem but a battery problem due to LG batteries having a bad batch and overall suck. I ordered a anker battery off of eBay and guess what? I have not had one single issue again for a week straight. Same rom and kernel as before. So to anyone having issues and are using the stock battery replace it with a non OEM brand.
Sent from my LG-P999 using xda premium
I was just about to post this! My 1550 mAh Anker battery lasts me from 6am to around 11pm when I charge it. Not only are any issues gone (sometimes had random reboots, maybe 3-4 times a week, nothing big but still annoying especially if I'm listening to music), but it also lasts maybe 2 hours longer for me than stock. Try this before you sell it. You'll regret it later of you don't. (;
Sent from my amazing G2X running Bionic Reloaded v1.2.1